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排序方式: 共有910条查询结果,搜索用时 150 毫秒
861.
Ahmed ElSayed Elif Kongar Ausif Mahmood Tarek Sobh 《Signal, Image and Video Processing》2018,12(7):1353-1360
Face recognition algorithms customarily utilize query faces captured from uncontrolled, in the wild, environments. The quality of these facial images is affected by various internal factors, including the quality of sensors used in outdoor cameras as well as external ones, such as the quality and direction of light. These factors adversely affect the overall quality of the captured images often causing blurring and/or low resolution, a phenomena commonly referred to as image degradation. Super-resolution algorithms are highly effective in improving the resolution of degraded images, more so if the captured face is small requiring scaling up. With this motivation, this research aims at demonstrating the effect of one of the state-of-the-art image super-resolution algorithms on the labeled faces in the wild (lfw) dataset. In this regard, several cases are analyzed to demonstrate the effectiveness of the super-resolution algorithm. Each case is then investigated independently comparing the order of execution before or after the 3D face alignment step. Following this, resulting images are tested on a closed set face recognition protocol using unsupervised algorithms with high-dimensional extracted features. The inclusion of super-resolution resulted in improvement in the recognition rate compared to unsupervised algorithm results reported in the literature. 相似文献
862.
Mahmood?Tavakoli Hafshejani Samira?SaeedniaEmail author Mehdi?Hatefi Ardakani Zahra?Pakdin Parizi 《Transition Metal Chemistry》2018,43(7):579-589
A magnetically recoverable nanocatalyst was synthesized by covalent binding of a Schiff base ligand, namely N,N′-bis(Salicylidene)-1,3-diaminopropane-2-ol (H2salpn), onto the surface of silica-coated magnetic CuFe2O4 nanoparticles, followed by complexation with MnCl2. The resulting core–shell nanoparticles were characterized by spectroscopic and microscopic methods, including FTIR, XRD, VSM, TGA elemental analysis, TEM, and SEM. The Mn content was determined by ICP analysis. The nanoparticles were investigated as a catalyst for the selective oxidation of alcohols to the corresponding carbonyl compounds with tertiary-butyl hydrogen peroxide. The catalyst can be magnetically separated for reuse, with no noticeable loss of activity in subsequent reaction cycles. FTIR, VSM, and leaching experiments after three successive cycles confirmed that the catalyst was strongly anchored to the magnetic nanoparticles. A suitable mechanism for the reaction is proposed. 相似文献
863.
In this work, we propose an efficient selective retransmission method for multiple‐input and multiple‐output (MIMO) wireless systems under orthogonal frequency‐division multiplexing (OFDM) signaling. A typical received OFDM frame may have some symbols in error, which results in a retransmission of the entire frame. Such a retransmission is often unnecessary, and to avoid this, we propose a method to selectively retransmit symbols that correspond to poor‐quality subcarriers. We use the condition numbers of the subcarrier channel matrices of the MIMO‐OFDM system as a quality measure. The proposed scheme is embedded in the modulation layer and is independent of conventional hybrid automatic repeat request (HARQ) methods. The receiver integrates the original OFDM and the punctured retransmitted OFDM signals for more reliable detection. The targeted retransmission results in fewer negative acknowledgements from conventional HARQ algorithms, which results in increasing bandwidth and power efficiency. We investigate the efficacy of the proposed method for optimal and suboptimal receivers. The simulation results demonstrate the efficacy of the proposed method on throughput for MIMO‐OFDM systems. 相似文献
864.
Riccardo Costan Zovi Haroon Mahmood Andrea Dorigato Giulia Fredi Alessandro Pegoretti 《Molecules (Basel, Switzerland)》2020,25(22)
Thin cyclic olefin copolymer (COC) foils were used as intrinsic thermoplastic healing agents in carbon fiber (CF)-reinforced epoxy laminates. COC films were produced by hot pressing and were interleaved in the interlaminar regions between each EP/CF lamina, during the hand layup fabrication of the laminates. Three samples were produced, i.e., the neat EP/CF laminate without COC, and two laminates containing COC layers with a thickness of 44 μm and 77 μm, respectively. It was observed that the fiber volume fraction decreased, and the porosity increased with the introduction of COC layers, and this effect was more evident when thick films were used. These two effects, combined with the sub-optimal adhesion between COC and EP, caused a decrease in the mechanical properties (i.e., the elastic modulus, flexural strength, interlaminar shear strength and interlaminar fracture toughness) of the laminates. Specimens subjected to mode I interlaminar fracture toughness test were then thermally mended under pressure by resistive heating, through the Joule effect of conductive CFs. A temperature of approximately 190 °C was reached during the healing treatment. The healing efficiency was evaluated as the ratio of critical strain energy release rate (GIC) of the healed and virgin specimens. Healed specimens containing COC layers of 44 μm and 77 μm exhibited a healing efficiency of 164% and 100%, respectively. As expected, the healing treatment was not beneficial for the neat EP/CF laminate without COC, which experienced a healing efficiency of only 2%. This result proved the efficacy of COC layers as a healing agent for EP/CF laminates, and the effectiveness of resistive heating as a way to activate the intrinsic healing mechanism. 相似文献
865.
Marjan Mollazadeh Maryam Mohammadi-Khanaposhtani Homa Azizian Afsaneh Zonouzi Zahra Abdolahi Hamid Nadri Bagher Larijani Mahmood Biglar Mohammad Mahdavi 《中国化学会会志》2020,67(10):1910-1928
2,4-Dioxochroman-pyridinium-phenylacetamide derivatives 7a–n were synthesized and evaluated for their in vitro cholinesterase (ChE) inhibitory activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Obtained results demonstrated that, among the synthesized compounds, two compounds, 7j and 7k , were more potent than the standard drug donepezil against BuChE and did not show cytotoxicity and carcinogenicity. Furthermore, through molecular modeling and molecular dynamic studies. we showed that these compounds can be located deep in the gorge cavity of BuChE and that they interacted with catalytic residues, acyl, and cholin-binding pockets of this enzyme. Support information 相似文献
866.
Muhammad Yaqub Javeria Batool Khalid Mahmood Abida Ashraf Ruqayia Perveen Zahid Shafiq 《Journal of heterocyclic chemistry》2020,57(8):3089-3104
A regioselective and convenient methodology was developed to synthesize heterocyclic derivatives, bearing imidazole, piperidines, and azepines rings. The N-arylnitrones derived from 3-formylchromones were selected to react with heterocyclic ketene aminal to furnish the structurally attractive and pharmacologically important fused ring heterocycles. The N-arylnitrone moiety of 3-formylchromone was used to activate the formyl group for regioselective fused ring heterocycles synthesis, whereas, the effect of substituents at aryl functionality of nitrones were studied to improve the yield of target fused ring heterocyclic products. The synthesized compounds (10-12) were evaluated for their in vitro cytotoxic and antifungal influences. In cytotoxic (brine shrimp lethality) assay, compound 11e was found to be active with LD50 = 4.1 × 10−6 μg/mL. 相似文献
867.
Mahmood Jabareen 《PAMM》2014,14(1):351-352
A number of approaches for finite deformation elastoplasticity with different classes of kinematic decomposition have been published in the literature (e.g. additive split of the Lagrange strain, multiplicative split of the deformation gradient, additive split of the rate of deformation, etc.). In the present work, a general theoretical framework for modeling a smooth elastic inelastic transition for large deformations of rate independent elastic-plastic and rate dependent elastic-viscoplastic materials has been proposed. It is well known that in classical rate independent elastic-plastic models the transition from the elastic regime to the plastic regime is rather sharp, while in the present model this transition is smooth and both rate independent and rate dependent models are characterized by overstress. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
868.
Estimation of efficiency of firms in a non-competitive market characterized by heterogeneous inputs and outputs along with their varying prices is questionable when factor-based technology sets are used in data envelopment analysis (DEA). In this scenario, a value-based technology becomes an appropriate reference technology against which efficiency can be assessed. In this contribution, the value-based models of Tone (2002) are extended in a directional DEA set up to develop new directional cost- and revenue-based measures of efficiency, which are then decomposed into their respective directional value-based technical and allocative efficiencies. These new directional value-based measures are more general, and include the existing value-based measures as special cases. These measures satisfy several desirable properties of an ideal efficiency measure. These new measures are advantageous over the existing ones in terms of (1) their ability to satisfy the most important property of translation invariance; (2) choices over the use of suitable direction vectors in handling negative data; and (3) flexibility in providing the decision makers with the option of specifying preferable direction vectors to incorporate their preferences. Finally, under the condition of no prior unit price information, a directional value-based measure of profit inefficiency is developed for firms whose underlying objectives are profit maximization. For an illustrative empirical application, our new measures are applied to a real-life data set of 50 US banks to draw inferences about the production correspondence of banking industry. 相似文献
869.
The propagation of linear and nonlinear dust ion acoustic waves (DIAWs) are studied in a collisionless magnetized plasma which consists of warm ions having anisotropic thermal pressure, nonthermal (energetic) electrons and static dust particles of positive and negative charge polarity. The anisotropic ion pressure is defined using double adiabatic Chew‐Golberger‐Low (CGL) theory. In the linear regime, the propagation properties of the two possible modes are investigated via ion pressure anisotropy, dust particle polarity and nonthermality of electrons. Using reductive method Zakharov‐Kuznetsov (ZK) equation is derived for the propagation of two dimensional electrostatic dust ion acoustic solitary waves in dusty plasmas. It is found that both compressive and rarefactive solitons are formed in presence of nonthermal electrons using Cairn's distribution [R.A. Cairns, A.A. Mamun, R. Bingham, R.O. Dendy, R. Bostrom, C.M.C. Nairn and P.K. Shukla, Geophys.Res. Lett. 22 , 2709 (1995)] in the system. The ion pressure anisotropy, nonthermality of electrons and charge polarity of the dust particles have significant effects on the amplitude and width of the dust ion acoustic solitary waves in such anisotropic nonthermal magnetized dusty plasmas. The numerical results are also presented for illustration. Our finding is applicable to space dusty plasma regimes having anisotropic ion pressure and nonthermal electrons. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
870.
In this paper, the characteristic matrix method is used to study the propagation of electromagnetic waves through one-dimensional lossy photonic crystals composed of negative and positive refractive index material layers with symmetric and asymmetric geometric structures with a defect layer at the center of the structure. First, the positive index material defect layer is considered, and the effects of the polarization and the angle of incidence on the defect mode in the transmission spectra of the both structures are investigated. The results show that the number of the defect modes in the transmission spectra depends on the geometry (symmetric or asymmetric) of the structure. In addition, it is shown that the defect mode frequency increases as the angle of incidence increases. This property is independent of the geometry of the structure. Then, for normal incidence, the negative index material defect layer is considered, and the properties of defect modes for both structures are investigated. The results can lead to designing new types of transmission narrow filters. 相似文献